Attachment for radio receiving sets



June 5, 1928.

P. MERTES, JR

ATTACHMENT FOR RADIO RECEIVING SETS Filed Fe b. 5, 1927 IN VEN 'T'OR.

692% y, BY

c/Z TTOR-NEY.

Patented June 5, 192 8.

PATENT OFFICE.

PETER MERTES, JR., OF ST. PAUL, MINNESOTA.

ATTACHMENT FOR RADIO RECEIVING SETS.

Application filed February 5, 1927. Serial No. 166,104.

'M'yinvention relates to an attachment or auxiliary device for radio receiving sets and the object is to provide a simple, highly ellicient. device which eliminates the use of an antenna with any set; a further object being to provide for positive. selection of reception according to wave lengths, said wave lengths commonly designated by .meters.

One result in the use of my device is greatly increased clearness and volume of tone in the receiving set.

I In ,the accompanying drawing Fig. 1 is a partly sectional top view of a horizontal type of my device adapted for 16 mounting ina radio paneLf.

ig. 2 is a sectional detail as on line 2-2 ofFig.1.@" r Fig. 3 is an enlarged sectional detail as on line 33 in'Fig. 2 showing mounting of a preferred type of contact clips used in my coil construction.

Fig. 4 is a top view and Fig. 5 a partly sectional side elevation of a vertical type of my device.

Fig. 6 is a circuit diagram of'my coil and adjacent parts of a receiving set including the first stage in the power tube of said set.

Referring to the drawing by reference numerals, 10 is the vertical front panel of a radio receiving cabinet the part of it shown being in proximity to the usual dials of the radio set (not shown). Referring particularly to Figs. 1 and 2, 11 is an aperture in panel 10 through which the center bearing 12 of a web casting 12 projects forwardly and its outer part threaded for nuts 13, said web having a circular flange 12 which retains and centers the front'end of an elongated cylinder 14. The rear end of said cylinderld is closedby a removable cap 15 bored centrally for a removably fixed,

threaded rod 16 the rear exposed end of which is adapted to receive the jam nuts 17; thefront end of said rod projecting forward of thebore of'web 12 and having a head 16 On said head is suitably fixed as at 19 a rotary dial 18 with a manipulating button 20.

14* are a number of longitudinal, integral, parallel ribs of cylinder 14 on the inner side of the latter. Said ribs constitute guides for an insulated crosshead 21 having I receive and retain forked ends closed about the wire.

' poses.

a central threaded collar 22 engaging the threaded rod 16, said collar 22 fixed in said crosshead by means of jam nuts 22 and adapted to move the'latter according to rotation of dial 18. v

23 are close wound coils of a singleinsulated wire wound on the cylinder 14 throughout its length, the front end of said wire fixed to the grounded side of the radio set as at 14* (see also Fig. 6) and the rear end fixed to a contact 25 and thence preferably extending as le to the antenna side of the receiving set .(Fig. 6). For each rib 14 the crosshead 21 is provided with a radial bore 26 having an electroconductivc ball 27 and a coiled pressure spring 28 back of it normally pressing the ball against the top of'a rib 14 29 are a series of contact clips each with a head portion 29 exposed inwardly of rib 14 and having a double shank extended outwardly through the wall of cylinder 14 and the ends of said shank being forked (as at 29 in Fig. 3) to frictionally the wire 23 which is not 29 indicates the It will be understood that these wire retaining clip ends are arranged close together in each rib and all the ribs but the wire is tapped by a clip only for each one and a quarter turn or winding (four hundred and fifty degrees apart). When moving the crosshead by means of rotating the dial 18 it is obvious that only one ball at a time establishes a lead in contact from the coils through the ball 27 the spring 28 and thence through sleeve 22, the latter in turn transmitting current through screw rod 16 thence to plate 12, through an outer lateral flange 12 of said plate, through a contact 30 grounding current at 32 through wire 31 (see Figs. 1 and 6). The size of coil and winding are such that each contact 29 being spaced one and a quarter revolution from the next contact corresponds to one meter of wave length as computed for radio broadcasting pur- The crosshead starts movement from a position near the front panel at which time the adjacent receiving set is tuned in for receiving a broadcasting program of low wave lengths. I Moving the crosshead rearwardly estabinsulated at these points.

lishcs circuit as described through an increasing number of windings and which windings corresponds to the number of meters in the wave lengths of various broadcasting stations.

In Fig. 6 the coils 33 is the primary winding a nd 33 the secondary winding represent a radio transformer. 34 is a resistance connected at 35 to a power or vacuum tube 36 of a radio receiving set.

In the modified form shown in Figs. 4

and the device is mounted verticallythe rod 16 being vertically mounted but has no head as 16 theupper end being plain and retained within a bell-shaped rotatable shell 37 by means of a pin 38. The lower rim of shell 37 has suitable degree markings 37 which correspond to the metric wave lengths of" various broadcasting stations- These markings will passba suitable, stationary marker 40 on an insulated base 391 The said base has an integralcentral bearing or poclo et 39 within which the nuts 17 engage rod 16. 30 is a contact screw corresponding to screw 30 in Fig. 1 and through sa1d screw circuitis grounded as through the wire 31 in Fig. 1'. This form of the device serves two desirable purposes namely to'shield the coil and provide an independent attachment applicable to any receiving set, whereas the form shown in Figs. 1 and 2 are bullt-ln units of a rad o receiving set.

I claim:

In a radio receiving set, a tuning coil comprising a rotatably' mounted dial, a threaded shaft fixed to and concentric of ad dial, a cylinder fixed concentrically a out said shaft, an insulated wire wound in close coils on the exterior face of said cylinder, parts of said...wire exposed at predetermined spacings throughout its length, a number'of'longitudinally arranged circularly spaced ribs on the interior of said cylinder, said wire attachable at one end of an antenna wire, a crosshead threaded at its center to engage and be moved on the the dial and the other end ofsaid wire connected therewith and means for connecting sa1d web wlth a ground wire.

In testimony whereof I afiix my signature.

PETER MERTES, J R. 

